东天山地区金矿床成矿流体地球化学及其成矿机制

The mechanism of gold ore formation in the eastern Tianshan Mountains, Xinjiang Uygur Autonomous Region, that has been dealt with from various aspects, remains unclear. On the basis of investigations of regional geology, ore deposit geology, and microscopic observations of ores and related rocks of the Jinwozi, the 210, and the Mazhuangshan gold ore deposits, this thesis made a systematic research on the microthermometry of gangue quartz-hosted fluid inclusions, gas, liquid ion and rare earth element compositions and hydrogen, oxygen isotope compositions of sulfide- and quartz-hosted fluid inclusions, and sulfur and lead isotope compositions of sulfide ore minerals from the major ores in the three deposits. On the basis of the above synthetic studies, sources of ore-forming fluids and metals, and mechanism of gold ore formation in the region were discussed. Gas compositions of pyrite- and sphalerite-hosted fluid inclusions were first analyzed in this thesis. Compared with gangue quartz-hosted fluid inclusions, the sulfide-hosted ones are richer in gaseous species CO2, CO, and CH4 etc. Both gas and liquid CO2 are commonly observed in fluid inclusions, whereas halite daughter minerals rarely occur. Ore-forming fluids for the three gold ore deposits are characteristically of medium to low temperatures, medium to low salinities, are rich in CO2 and Na+, K+, Cl" ions. Gas covariation diagrams exhibit linear trends that are interpreted as reflecting mixing between the magamtic fluid and meteoric-derived groundwater. Regarding rare earth element compositions, the Jinwozi and the 210 deposits show moderate to strong LREE/HREE fractionations with negative Eu anomalies. However, the Mazhuangshan deposit shows little LREE/HREE fractionation with positive Eu anomalies. Hydrogen and oxygen isotope compositions of pyrite-hosted fluid inclusions that were first analyzed in this thesis indicate the presence of magmatic water. Hydrogen and oxygen isotope compositions of pyrite- and quartz-hosted fluid inclusions suggest mixing between magmatic water and meteoric-derived groundwater. Sulfur and lead isotope compositions of sulfide ore minerals indicate multi-sources for the metallogenetic materials that range from the crust to the mantle. On the basis of the above synthetic studies, genesis of the gold ore deposits in the eastern Tianshan Mountains was approached. From the Middle-Late Hercynian to Early Indosinian, geodynamic regime of the region was changing from the collisional compression to the post-collisional extension. During the period, magmas were derived from the crust and the mantle and carried metallogenetic materials. Magma intrusion in the upper crust released the magmatic fluids, and drove circulation of groundwater. Mixing of magmatic fluid with groundwater, and extraction of metallogenetic materials from the country rocks are the mechanism for the gold ore formation in the eastern Tianshan Mountains.